The invention relates to improvements in subfractional horsepower long-life electric motors.
Subfractional horsepower electric motors manufactured for long-life service are shown, for example, in U.S. Pat. No. 2,053,425. A typical application of such motors is for air circulation in refrigeration apparatus. Generally, such motors include bearing lubrication systems which provide for self-recirculation of a small quantity of oil to ensure a long service life and high reliability. It is critical in this type of motor that the original supply of oil be confined in a zone which is perfectly leak-proof because any leakage, however small, will eventually lead to premature failure of the motor. The oil circuitry may include an oil reservoir, a wick and oil grooves on a shaft or bearing to produce a supply of lubricant along the length of the bearing Typically, this oil supply and recirculation circuitry involves a number of parts and labor content that add to the cost of the motor In cold environments, the viscosity of the oil can make it difficult to ensure full lubrication so that premature failure of the bearing and therefore the motor may occur.
U.S. Pat. No. 4,746,828 illustrates an electric motor construction in which the end housings are injection molded plastic parts attached to a stack of stator laminations with tie rods running through the stack.